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Sleeping in Two Sessions

Due you find yourself waking up spontaneously in the middle of the night to a brief window of wakefulness where you are intellectually productive? If you sleep in two bulk sessions you are engaging in segmented sleep that is perfectly normal and healthy. 

Segmented sleep is defined by a sleep pattern with two distinct sleep periods separated by a brief window of wakefulness. Humans have long enjoyed segmented sleep and it was not until the start of the industrial revolution that segmented sleep patterns came under fire as being counter productive, soon to be widely described as dysfunction by sleep doctors when in fact segmented sleep is perfectly normal. If you experience segmented sleep you do not have insomnia as certain pharmaceutical companies might like you to believe.


Historically people have used this late night window of wakefulness to pray and contemplate their dreams while the dreams are still fresh in the memory. Segmented sleep patterns may actually be healthier than bulk consolidated sleep patterns. Studies point to stress and anxiety reduction in people that engage in segmented sleep schedules.

Eyes, Light and the Brain

Before the widespread use of artificial light the total amount of time people spent sleeping was actually greater. The brain has a daylight sensor system in the eyes. When the eyes are exposed to light the brain attempts to adjust its "active day length interval". Out brain has the ability to vary wakefulness intervals, and has historically done so to adapt total wakeful time to day length. Studies have actually show that the biological periodicity of sleep is affected by the type of light people are exposed to during the day. People that spend large portions of time in dimly lit indoor environments actually sleep almost 1 hour more than people that spend their day in bright environments with good natural spectrum light.

Lighting and Mood 

People with seasonal affective disorder frequently sit in-front of bright artificial light boxes to reduce depression and anxiety. The light in an environment can dramatically alter the feel of a given environment. High brightness levels increase wakefulness while low dim light tend to encourage relaxation and calmness. The way that light affects mood and cognition is well understood by lighting engineers. Many people can feel the weather because of the strong effect that lighting has on their mood. Dim grey overcast conditions cause many people to feel "gloomy" and this feeling goes into descriptions about the weather "gloomy winter". People that are regularly exposed to natural light tend to sleep better and sleep less. It seems that our brain enjoys bright light, and uses periods of exposure to bright light input signals from the eyes to affect chemical systems that regulate biological rhythms.

Levels of Consciousness

Altered states of consciousness are frequently experienced by people that daydream, and similar states of mental function are achieved in early morning or late night wakefulness windows. There is not a clear distinction between being asleep and being awake, there are different levels of wakefulness and different levels of sleep. Our consciousness ebbs and flows in and out of these states every day. The way we handle information differs throughout the day. Peak cognitive function is only achieved when a sufficient amount of physical fitness inducing activity has been performed. People that move more also tend to sleep better and enjoy more energy while they are awake.

Biological Functions of Sleep 

Sleep is an important biological activity that living beings perform to conserve biochemical energy during repair and maintenance phases that keep the body and mind in balanced working order.

Organizing Information Input and Storage

The brain uses sleep to consolidate memories; sorting, filtering, ranking and organizing memories for long term, medium term or short term storage and retrieval. Unlearning also occurs during sleep when the brain rejects information with low priority ranking. Unlearning is as important as learning because the brain needs to be able to reject useless information to focus on important ideas, concepts, feeling and choices. The processes of forgetting is essential to normal mental function, and I explored this in another posting.

Tissue / Bone Repair and Maintenance

The body uses deep sleep to perform tissue repair functions in all areas of the body. Bones for example are constantly being taken apart and rebuilt by specialized cells that the brain regulates with signaling hormones. During sleep the brain is able to perform chemical control balancing algorithms to take the body through different phases where different biochemical repair and maintenance functions take place.


Deep stage 4 sleep is associated with deep tissue repair whereas the lighter stages of sleep provide for dreaming and mental balancing. Dreams are abstract psychological information balancing events that affect memory formation, and post sensory information buffer processing. When you think of the brain and body as a computer controlled bio chemical system it makes sense that the body has to go into a low power mode for repair and maintenance of all the subsystems in the body and of the information processing and handling systems in the brain.

Healthy Brain Chemistry

The human brain is a super efficient super powerful intelligent information processing engine that also controls complex motor control and chemical control functions of the body. The brain has a metabolic system and produces a wide array of important chemical control agents that regulate the tissues of the brain and body. Neurotransmitter systems for example are synthesized by specialized cells in certain neuron tissues, and this system of brain chemicals has to be re-balanced during sleep. Stockpiles of these mood regulating chemicals are restored during sleep so that enough presynaptic vesicles are formed to maintain healthy mental function during wakeful time. The brain releases stress reducing chemicals during sleep that help to calm the mind and body.

Cleaning up Unwanted Byproducts 

Our brains produce waste products, metabolites, broken proteins, and other mental sludge when we are up and about in the world thinking and doing things. At night when we sleep, the brain ramps up it cleaning processes, to flush our braincells so that the liver can filter the brain fluids that were used to clean metabolites out of the brain. I recently learned about this from an article posted on The Verge. They were reporting on recent sleep research done at a University in New York. This information builds upon my main thesis here about the biological role of sleep in maintaining a healthy brain and body. Have a look at the article

Expanding Knowledge about Sleep

Our understanding of the biochemical importance of sleep is still developing. Every year scientists unlock more secrets that explain the structural and functional aspects of the brain, its information processing, sleep and biological control functions that govern the body. The brain is an amazing organ, and sleep is essential for overall health. By keeping the brain balanced, sleep not only keeps our moods stable, it also cover control of the repair system that are constantly maintaining all of the organs and biochemical systems in the body.

Get some sleep. Sleep deprivation is toxic and harmful. Everyone must sleep, and sleeping deeply enables your body to self repair more efficiently. Our bodies are made of endlessly recycled star dust that is constantly under construction.

Your segmented sleep schedule is biologically normal, so rest easy knowing that is is normal and healthy to have a wakeful window in the middle of the night.

Thinking About It

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